OpenVZ vs KVM Virtualization : Which is Best for Cloud Server

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It is Quite Frequently Asked Which is Best Virtualization for Cloud Server. Here is OpenVZ vs KVM Virtualization Comparison from Usage POV. OpenVZ is container-based virtualization, whereas KVM is a hardware virtualization technology. Comparing them head to head as OpenVZ vs KVM is actually impractical from theoretical point of view. OpenVZ stands for Open Virtuozzo. OpenVZ and for Open Virtuozzo are products of Parallels, a virtualization technology company. KVM stands for Kernel-based Virtual Machine.

OpenVZ vs KVM Virtualization : What the Technologies Behind Them in Plain English?

OpenVZ is container based virtualization for Linux, in other way we can say that OpenVZ is OS-level virtualization. In operating system level virtualization some basic components exist once on the server and are used by all the guests. In other words, each guest is a container, which shares the same underlying operating system but still operates as secure, isolated environment. Each can performs like a normal stand-alone server.

KVM is true virtualization, each guest is independent of the host. OpenVZ is a container virtualization which relies on the host node kernel. KVM has no restrictions in terms of functionality. No restrictions comes with the price of more overhead in case of KVM. KVM is generally more stable than OpenVZ. KVM, however is not a dedicated environment. In both cases the virtualizations have to share host CPU and network ports.

KVM or Xen will cost higher – because host can not oversell, some resources are lost etc. Approximately $10/1GB is the standard price of KVM virtualization based cloud servers. There are cheaper Dedicated Servers.

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OpenVZ vs KVM Virtualization : Which Performs Better? Is there Any Limitations?

Oddly, OpenVZ performs far better than KVM despite lesser cost of the former. The major problem with OpenVZ is that, OpenVZ does not provide the features which KVM does. Like, for example TUN/TAP, reverse DNS, fuse, ip_conntrack support often needs to asking the provider by opening a ticket. Technically it is possible to run Docker inside OpenVZ but commonly the hosts do not allow that compromised mode of running Docker. With OpenVZ, host may ask to keep the load average within a limit.

In case of KVM or Xen, you are actually getting full set of control – like DigitalOcean, Linode, Rackspace, Softlayer provides to the end consumer. KVM supports paravirtualization for device drivers, which improves I/O performances. However, OpenVZ still performs far better due to lesser overhead.

Lesser data security, chance of vanishing data is more in OpenVZ. However, Xen or KVM can vanish data too. These chances are very less and in any public server, you need few hourly backup. It is better to wait for few hours after provisioning of OpenVZ virtual server. Data may get vanished during the initial few minutes period.

OpenVZ vs KVM Virtualization : Which is Best for Cloud Server

Cloud Server typically were not OpenVZ. In 2014, Parallels announced that they’ll will be merging its open-source OpenVZ and proprietary Parallels Cloud Server projects. KVM technically run all the applications like that on a dedicated server, migrating from virtual machine to dedicated server from operating system level is possible in case of KVM. For running WordPress like common MySQL and PHP web softwares, OpenVZ in hand of a good host’s better sysadmins will deliver dedicated server like performance at front end. KVM or Xen are good for some usage which are not possible on OpenVZ but cost of dedicated server is not possible to bear. OpenVZ is usually not liked by the hosting providers, it is difficult to manage by the sysadmins.

KVM, Xen honestly are not needed for ordinary works or normal websites. When so much dedicated resources is needed, it is sane to use a dedicated server. There are funny advantages of OpenVZ. Host’s sysadmin can interrupt an attack, reset firewall, login to install softwares etceteras more easily.

OpenVZ memory is measured in terms of virtual memory pages allocated. Buffer cache is not part of the container configuration. Hitting memory limit faster is not abnormal. Factually OpenVZ more dependent on the quality of service by the host & sysadmin.